Study calls colors of fossilized animals into question

In a study published March 27 in the journal “Biology Letters,” a group of Yale geology and geophysics researchers found that the common method of reconstructing the feather color of fossilized birds is flawed. In the past, scientists examined the shape and structure of melanosomes — cellular structures containing the compound melanin, which determines the color of feathers. Though scientists have typically assumed that the melanin remained unchanged, the study showed this assumption to be incorrect, said study co-author Zhengrong Wang, a Yale geology and geophysics assistant professor.

Lead researcher Maria E. McNamara — a former Yale postdoctoral researcher now working at the University of Bristol — simulated the fossilization process in her lab using a machine called an autoclave. The autoclave generates very high temperatures and pressures in order to mimic the conditions deep inside the Earth’s crust. McNamara and her team, which included Peabody Museum Director Derek Briggs, have found that scientists cannot reconstruct color using melanosomes alone because geological processes alter their original structure over time.

“We’ve been taking modern feathers and placing them in the autoclave,” McNamara said. “What we’ve found is that when all of these feathers went into the experiments, they came out black. All the other color-producing structures were destroyed.”

Scientists will now have to go back and reexamine their samples, researchers said.

“All those beautiful colors we see in prehistoric sci-fi movies are based on these predictions,” Wang added.

Both McNamara and Wang said the importance of understanding animal color cannot be understated. Color often has specific evolutionary functions — such as camouflage, warning signals, mating or communication — that can tell scientists a lot about how an animal behaved, McNamara said.

Yale geology and geophysics assistant professor Kanani Lee, who was not involved in the study, said she attended a talk McNamara gave last year in which she showed similar findings for the shell colors of fossilized beetles.

“She was looking at bugs,” Lee said, “and what was kind of cool about it is that she saw that in the lab, if she influenced the pressure and temperature conditions, she could change what the colors would look like.”

Wang said the team’s findings were unexpected, adding that he is excited about the potential consumer applications of this research. Currently, companies use metals like lead to create colorful toys for children, but this process can cause major health problems.

“If we know how to make color from organic material, we don’t have to use metals to produce color anymore,” Wang said.

The research was funded by a Marie Curie International Mobility Fellowship through University College Dublin.